I saw a link to this on the Mach3 Yahoo Forum a few days back and finally got a chance to write it up. This also reminded me of a post I saw on hackaday using different technique.

The first technique extrudes cement in a fluid state in layers. The current results appear to be of mixed quality and they are clearly in a refinement mode. The use appears to be geared for artistic work rather than actual contruction. The whole thing is controlled via Mach3.

The next technique works similar to a RepRap machine. It first lays down a layer of sand at a 25 DPI resolution, then lays down a binder. It sounds like the machine is a bit frustrating for the inventor right now, but he is producing some good looking results already.